Comparative Densities of Beech Scale, Cryptococcus fagisuga, (Hemiptera: Eriococcidae) in the Country of Georgia and Massachusetts (USA), Parts of its Native and Invaded Ranges, on two Species of Beech

R. G. Van Driesche, G. Japoshvili

Abstract

The Caucasus Mountains in the country of Georgia are part of the native range of beech scale (Cryptococcus fagisuga) and Massachusetts (United States) is part of the invaded range of this species. As background to determine if the native range of this scale might be a source of natural enemies useful for correcting the ecological damage caused by beech scale in North America to America beech (Fagus grandifolia) comparative scale densities were measured in both locations in natural forest stands of F. grandifolia in Massachusetts and F. orientalis in Georgia. Average diameter at breast height (DBH) and health values were also compared. Scale densities were found to be 45.4-fold higher per unit area of bark in Massachusetts on F. grandifolia than in the country of Georgia on F. orientalis. Also, F. orientalis trees at sample sites in Georgia were 2.9-fold larger in DBH and much healthier that were F. grandifolia trees in Massachusetts. These data suggest that either F. orientalis is more resistant to beech bark disease than F. grandifolia or key natural enemies found in Georgia are missing in Massachusetts, or both. Cage exclusion studies are underway, separate from results reported here, to separate the effects of tree resistance and natural enemies.